Information recording/reproducing apparatus

ABSTRACT

A playback error associated with overwriting on a narrow-width track is prevented from occurring in the overwritten portion. A signal generator ( 11 ) generates a signal of a predetermined data pattern that stabilizes the operation of a synchronizing pulse generator of a playback system (shown in a separate figure). A timing generator ( 4 ) switches over a switch ( 12 ) to the output of the signal generator ( 11 ), at least a period of time equivalent to writing of one track before the main signal is input. When a signal of the predetermined data pattern from the signal generator ( 11 ) has been output, the timing generator ( 4 ) switches over the switch ( 12 ) to the main signal. The playback system includes a circuit which discriminates between the predetermined data pattern and the main signal data from a playback signal generated by playing back a record on a magnetic tape (T).

TECHNICAL FIELD

[0001] The present invention relates to information recording andplayback apparatuses and specifically to an information recording andplayback apparatus for preventing a playback error in an overwrittenportion associated with an increase in recording density achieved bynarrowing the track width of a magnetic tape apparatus.

BACKGROUND ART

[0002] A typical apparatus for reading and writing information throughsequential access, such as a magnetic tape recording and playbackapparatus, reads and writes information for every track and thereforerequires highly precise tracking (track following function) duringrecording and playback of information. In playback mode, the range ofthe track width corresponds to the scanning area of a playback head.

[0003] Such high-precision tracking is also required during overwriting(writing new information to an already-written tape), and a portionchanged by overwriting is also processed for every track.

[0004] A high density is achieved by narrowing the minimum writing unit(track width); a narrowed track width, however, often preventssuccessful tracking.

[0005] In response to recent demands for recording media with increasedstorage capacity, the effective track width is narrower than the widthof the scanning area of the playback head, inevitably causing the widthof the scanning area of the playback head to span two contiguous tracksin some cases.

[0006] Unfortunately, a conventional information recording and playbackapparatus often generates an error during playback due to a narrowedtrack width if the width of the scanning area of the playback head spanstwo contiguous tracks, especially if one of the two contiguous tracks isan already-written track and the other is a newly written track.

[0007] The mechanism of the generation of the error described above isas follows: narrow-width tracks cause a track in a newly written portionto shift with respect to the original track or causes the frequency ofrecorded tracks to differ between the newly written portion and theoriginal portion due to differences in the recording system duringrecording, leading to poor frequency-locking of a phase locked loop(PLL) used in the playback system and finally to loss ofsynchronization. In short, such an error results from mixing of oldoriginal data and newly written data or a malfunction of the PLL.

[0008] In order to solve these shortcomings associated with theconventional information recording and playback apparatus, an object ofthe present invention is to provide an information recording andplayback apparatus for preventing the generation of a playback error ina portion of narrow-width tracks having information overwritten thereon.

DISCLOSURE OF INVENTION

[0009] In order to solve the shortcomings described above, the presentinvention provides an information recording and playback apparatus usinga magnetic tape as a recoding medium, comprising signal addition meansfor adding a predetermined data pattern to the leading end of main datato be recorded onto the magnetic tape during recording, thepredetermined data pattern stabilizing the operation ofsynchronizing-pulse supply means of a playback system; data recordingmeans for recording data generated by the signal addition means onto themagnetic tape; and data discrimination means for discriminating, duringplayback, between the recorded predetermined data pattern and therecorded main data from a playback signal generated by playing back arecord on the magnetic tape.

[0010] The present invention is achieved by the recording system and theplayback system as described below. In overwriting (writing new data onold data) mode, the recording system allows the predetermined datapattern for one track (track-pattern data) to be additionally written atthe leading end of the newly written data, the predetermined datapattern stabilizing the operation of the synchronizing-pulse supplymeans (hereinafter referred to as PLL) used in the playback system. Inplayback mode of the newly written data, the playback system allows thePLL to receive a playback signal which includes a signal component ofthe predetermined data pattern. These features ensure that an accurateclock for playback synchronization is generated by the PLL of theplayback system from the beginning of playback of the newly writtendata, preventing the generation of an error during playback of the newlywritten data.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a block diagram of a recording system of an informationrecording and playback apparatus according to an embodiment of thepresent invention.

[0012]FIG. 2 is a block diagram of a playback system of the informationrecording and playback apparatus according to the embodiment of thepresent invention.

[0013]FIG. 3 is an illustration in which a head of the playback systemscans over the track information recorded on a magnetic tape by therecording system of the information recording and playback apparatusaccording to the embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] An embodiment of the present invention will now be described withreference to the drawings.

[0015]FIG. 1 is a block diagram of a recording system of an informationrecording and playback apparatus according to the embodiment of thepresent invention.

[0016] The recording system of the information recording and playbackapparatus according to the embodiment includes a signal adder 1 (signaladdition means) which adds a predetermined data pattern to main signaldata; a recording-signal processing circuit 2 (data recording means)which converts an internal signal (an additional signal component of thepredetermined data pattern and a signal component of the main signaldata) of data to be written into a recording signal; a recording head 3(data recording means) which records the data to be written based on theinput recording signal; and a timing generator 4 which determines thetiming for adding the predetermined data pattern to the main signaldata.

[0017] The signal adder 1 includes a signal generator 11 (signalgeneration means) which generates a signal of the predetermined datapattern and a switch 12 (switching means) which toggles between the mainsignal (data) and the additional signal of the predetermined datapattern.

[0018] In FIG. 1, symbol T denotes a tape (magnetic tape) as a recordingmedium.

[0019] The recording-signal processing circuit 2 may, for example, be aD/A converter and others.

[0020]FIG. 2 is a block diagram of a playback system of the informationrecording and playback apparatus according to the embodiment of thepresent invention.

[0021] The playback system of the information recording and playbackapparatus according to the embodiment includes a playback head 21 whichconverts data recorded on the tape T to a playback signal; aplayback-signal processing circuit 22 which converts the playback signalto an internal signal; an A/D converter 23 which performs A/D conversionof the internal signal output by the playback-signal processing circuit22; a PLL 24 which extracts a clock from the internal signal output bythe playback-signal processing circuit 22 and then supplies the A/Dconverter 23 with the extracted clock; and a signal discriminationcircuit 25 (data discrimination means) which discriminates between thesignal of the main signal data and the signal of the predetermined datapattern from the signal output by the A/D converter 23.

[0022] The operation of the information recording and playback apparatusaccording to the embodiment will now be described with reference toFIGS. 1 and 2.

[0023] First, the operation of the recording system will be describedwith reference to FIG. 1.

[0024] To record data on the tape T, the signal adder 1, which hasreceived the main signal of the data, adds a signal of the predetermineddata pattern to the leading end of this main data and sends theresultant signal to the recording-signal processing circuit 2.

[0025] More specifically, an external system for sending the data sendsa data writing notification to an input line (not shown in FIG. 1) ofthe timing generator 4, at least a period of time equivalent to writingof one track before sending the data.

[0026] Upon receiving the notification, the timing generator 4 switchesover the switch 12 of the signal adder 1 to the signal generator 11. Asa result, a signal of the predetermined data pattern generated by thesignal generator 11 of the signal adder 1 is sent to therecording-signal processing circuit 2. After the time equivalent towriting of one track has elapsed, the timing generator 4 operates theswitch 12 so that the recording-signal processing circuit 2 receives themain signal.

[0027] The signal of the predetermined data pattern generated by thesignal generator 11 of the signal adder 1 may be of any kind that can bedetected with high sensitivity by the PLL 24 of the playback systemdescribed later and that can stabilize the operation of the PLL 24,which is capable of stably supplying an accurate clock when receivingthe signal. For example, the signal has a stripe pattern consisting oftwo different values repeated alternately and regularly (2T pattern).

[0028] The recording-signal processing circuit 2 converts the signal ofthe predetermined data pattern generated by the signal generator 11 ofthe signal adder 1 and the subsequent main signal to a signal forplayback and then sends the signal for playback to the recording head 3.This conversion may include D/A conversion and modulation.

[0029] The recording head 3 then records the signal for playback on thetape T.

[0030] The operation of the playback system (a counterpart of therecording system described above) will be described with reference toFIG. 2.

[0031] First, the playback head 21 converts data recorded on the tape Tto a signal for playback and then sends the signal for playback to theprocessing circuit 22.

[0032] The processing circuit 22 converts the sent signal for playbackto the internal signal and then sends the internal signal to the A/Dconverter 23 and the PLL 24.

[0033] The A/D converter 23 performs A/D conversion of the sent internalsignal using the clock sent by the PLL 24 and then sends the resultantsignal to the signal discrimination circuit 25.

[0034] The PLL 24 generates the clock (synchronizing clock) from theinternal signal sent by the processing circuit 22 and sends the clock tothe A/D converter 23. This internal signal includes the signal componentof the predetermined data pattern recorded by the relevant recordingsystem, in which the signal component of the predetermined data patternis added to the leading end of the signal component of the written data,thereby allowing the PLL 24 to ensure the generation of an accurateclock.

[0035] The signal discrimination circuit 25, which is characteristic tothe playback system of the present invention, discriminates between thepredetermined data pattern and the subsequent written data from theinternal digital signal sent by the A/D converter 23. The extractedpredetermined data pattern may be discarded.

[0036]FIG. 3 is an illustration in which the head of the playback systemscans over the track information recorded on the magnetic tape by therecording system of the information recording and playback apparatusaccording to the embodiment of the present invention.

[0037]FIG. 3 is an illustration in which newly written tracks aregenerated by overwriting on tracks which have been written before therecording by the recording system.

[0038] A 2T-pattern-recorded track (T2) is provided with recorded dataof the predetermined pattern, which is a stripe pattern consisting oftwo different values repeated alternately and regularly (2T pattern). Arecorded track (T1) is a track already recorded before overwriting andis contiguous to the 2T-pattern-recorded track (T2).

[0039] Playback-head scanning area SA (area scanned by the playback head21) spans the recorded track (T1) and the 2T-pattern-recorded track(T2), often generating an error in a playback system of a conventionalinformation recording and playback apparatus. The present invention,however, prevents the generation of an error at this portion and thesubsequent portions by recording onto the 2T-pattern-recorded track (T2)a predetermined data pattern that can be easily detected by the PLL 24.

[0040] The embodiment of the present invention has been described inrelation to the recording head 3 of the recording system, the recordinghead 3 writing new data on the already-recorded tape T; in general,however, the recording head 3 of the information recording and playbackapparatus according to the embodiment of the present invention allowsdata to be recorded onto the tape T having no information recordedthereon (virgin tape) in the same manner as for overwriting.

[0041] As described above, additional data for one track is written atthe leading end of data to be newly written during the overwritingprocess by the recording system, the additional data (predetermined datapattern) facilitating synchronization by the PLL used in the playbacksystem. Furthermore, a playback signal which includes a signal componentof the predetermined data pattern is input to the PLL during playback ofthe newly written data by the playback system, and thereby an accurateclock for playback synchronization is generated by the PLL of theplayback system from the beginning of playback of the newly writtendata. Thus, the present invention prevents the generation of an errorduring playback of the newly written data.

1. An information recording apparatus using a magnetic tape as a recording medium, the apparatus comprising: signal addition means for adding a predetermined data pattern to the leading end of main data to be recorded onto the magnetic tape during recording; and data recording means for recording the data generated by the signal addition means onto the magnetic tape.
 2. An information playback apparatus for playing back a magnetic tape having an additional predetermined data pattern at the leading end of recorded main data, the apparatus comprising: data discrimination means for discriminating between the recorded main data and the recorded predetermined data pattern from a playback signal generated by playing back a record on the magnetic tape.
 3. The information recording apparatus according to claim 1, wherein the predetermined data pattern for at least one track is added.
 4. The information recording apparatus according to claim 1, wherein the predetermined data pattern is a stripe pattern consisting of two different values repeated alternately and regularly.
 5. The information recording apparatus according to claim 4, wherein the stripe pattern is a 2T pattern.
 6. The information recording apparatus according to claim 1, wherein the signal addition means comprises: signal generation means for generating a signal of the predetermined data pattern; and switching means for toggling between a signal of the data to be recorded onto the magnetic tape and a signal of the predetermined data pattern.
 7. The information recording apparatus according to claim 1, wherein the magnetic tape is a magnetic tape any portion of which has written data or a magnetic tape no portion of which has written data.
 8. A method for recording information using a magnetic tape as a recording medium, the method comprising the steps of: adding a predetermined data pattern to the leading end of main data to be recorded onto the magnetic tape during recording; and recording data generated in the preceding step onto the magnetic tape.
 9. A method for playing back information on a magnetic tape having an additional predetermined data pattern at the leading end of recorded main data, the method comprising the step of discriminating between the recorded main data and the recorded predetermined data pattern from a playback signal generated by playing back a record on the magnetic tape. 